Glossary
Core Concepts
Phase Angle
Continuous measure (0-360°) of the skier's position within the compression/extension cycle relative to mogul terrain. 0° = maximum compression at crest, 180° = maximum extension in trough.
NTZ (Next Turn Zone)
A region of the mogul field representing where the nth upcoming turn might occur. NTZ-0 = current turn, NTZ-1 = next turn, NTZ-2 = two turns ahead, etc.
PTL (Potential Turn Location)
A place in the mogul field where a turn could physically occur — essentially the troughs between moguls.
Eye Tracking
Fixation
Gaze held on a location, measured by Pupil Labs glasses. Indicates where the skier is actively looking.
Saccade
Rapid eye movement between fixation points. The quick jumps between where you're looking.
Sensors & Data
IMU (Inertial Measurement Unit)
Accelerometer + gyroscope sensor embedded in Pupil Labs glasses. Measures head/body motion to derive phase angle.
Quaternion
Mathematical representation of 3D rotation, output from the IMU. Used to track head orientation.
Data Hierarchy
Mission
A ski trip or data collection expedition (e.g., "Tahoe 2025").
Session
One skier's data collection within a day — may include multiple runs.
Run
A single descent down the mogul field, typically ~10 minutes.
Segment
Contiguous period of skiing or stationary viewing within a run. Turn numbers reset per segment.
Frame
A single timestamp combining video frame, IMU data, and gaze coordinates.